Telephone-exchange system.



E. R. CORWIN.

TELEPHONE EXCHANGE SYSTEM APPLIOATION FILED E. 17. 1900.

1,040,634. Patented 0012.8, 1912.

:.:::.' i, wwwwwmw llfzfnesses: u: ,lrz erziok' UT. 3 TE ATET OFFIGEQ ELMER R. COLILWIMAOF CHICAGO, ILLINOIS, nsslelnon To 001mm TELEPHONE MANU-j FACTURING COMPANY, OF cmcaeo, ILLINOISQA'QORPORATION OF ILLINOIS."

TELEPHONE-EXCHANGE SYSTEM.

oaoy'csai Specification of'LettersIfatent. A Patented Oct. 8 1912,

Application filed March 17, 1909. Serial No. 483327.

To all whom "it may concern:

Be it known that I, Emma R. Gonwns, citizen of the United'states, residing at Chicago -in the county-'of Cook and State of Illinois, havednventcd a 'certain new and useful Improvement in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description, reference btlllg had to the accompai'iying draw-g 1 receiver, in rising, opens the bell bridge and ings," forming a' part of this specification.

My invention relates to telephone e 2- change systems, and relates nioreparticin. larly to trunk linaeqinpinent employed for uniting substationswhose lines extend to diflerent exchanges. Among the QbJQCtS o't my invention are,

' first,-'the p'rovision'of a trunk circuit: extending between exchanges, which serves lllQ- tallic'ally to separate the batteries at the two exchai'iges; second, the provision of means whereby proper control is had over supen visory apparatus where a trunk circuit tultilling the first object of my invention is employed; a

I will explain my'invcntion more fully by reference to the accompanying drawing, showing the preterrcd ei'nbodiment thereof, in which I have suggested, at A, one

change, at B, another-excliange, andat C, a

' extends between the sleeve contact jack 7) and the sleeve of the plugc.

trunk line equipment, all but the portion tillGltOflitiVing the jack and the signaling mechanism associated with the jaclt being understood to be at theexehange B, the said trunk line jack and the signaling apparatus associated with said jack being understood to be at the exchange A. At the exchange A, I have shown jack switches belonging to the lines oftwo subscribers M, N, one of many cord circuits a, and a group ot multipled trunk line jacks I) having sleeve andv tip cont-acts, which are connected or adapted for connection respectively with the tip contact of the trunk plug a and the sleeve contact of such trunk plug, the conductor (l extending between the tip spring of the jack band the tipof the plug a, while the (30l1(ltl(?0li' e 0 he i Before describing the mechanism and circuits of the trunk circuit intervening between the terminals 7) and c of the trunk circuit (the terminal I: being at exchange A and the terminal a at exchange B), I will change, B. Each of the telephone sub-stations shownin association with the exchange I; has a telephone switch-hook 1- adapted.

when holding the receiver 2, call bell 3.1 11 bridge of the limbs 4,-5 of each line, in which bridge isincluded a condenser to include a $6. Other ,snb station"outfits may beused.

l \Vhen the s \\'itch-hook at each station is re lieved ot the telephone receiver thcreat, the

3 includes the telephone transmitter 7 in series wlth the luiib's 4, 5 (it-the associate telephonev of the telephone receiver. 'l he limb l of each telephone line includes-an electroanag net or relay winding 9' and the limb 5 cl? each telephone line includes an electro-1nagnet or relay winding 10, the windings l) and 1 '10 being upon a common magnetic core. The limbs of the telephone lines are united by a common battery 1.1, whereby when a a receiver is removed from its switch-hook at a calling substation,"the windings f) and LO are energized, and inasmuch as these fwiiidings are cumulatively wound, the

icore of said windings is caused 'to operate iaii ariiiatui'e 12, which serves to include a isignal device, preferably a lamp 13, in a circuit which may be traced from the upper lterminal of the-battery 11 to the alternate i contact of the armature 12 (by way of imechanism which will be mentioned later,

.the subscriber whose line corresponds to the- ;lamp i3--desires to initiate a call; i

\Vhen two of the subscribers whose lines terminate at the exchange B desiie'connecline and in series with the receiver 2,-an lll'l pedance coil 8 being then included in shunttion with each other, they may bcunitcd by suitablecord connecting apparatus, such as ,indicated at 18. If a-subscriber whose line is associated with the exchangefli desires connection with a subscriber whose line is associated with the exchange B, thetrunk circuit having the terminals 7) (1 is brought. 'into service, the ternnnals ct acord connect-- ing circuit a being engaged :with the trunk 35 jack of a called line (the line P), the condiline ackt and a ot a calling subscriber I whose line extends tothe exchange A, while the terminal plug c of the trunk circuit-is I engaged'with .the jack ofacalled subscriber whos'e line extends to the exchange-B, and

in order-more clearly to understand the de-' scription which istto'follow, I- will at present omit a -'descr iption of the operations jack, the sleeve of such plug engaging the- -By inserting the plug 0 within the jack of a called subscriber, the tip of the plug 0 iscaused to engage the'line spring 19 of such a spring 20'of said jack (the springs'19 and 20 constituting talking contact terminals of the called line) while the heel or body of the plug 0 engages the thimble 15. The spring contacts 14 and 19 are mechanically con; nected, so that when the tip of the plug 0 engages and holds up the tip line spring 19,-

the-contact spring 14: is elevated and maintainedelevated during the presence of the plug 0 in the engaging jack, to disconnect thecontact 14 from the thimble 15 and bring and maintain said contact 14 in engagementwith an alternate contact, so that the signal device 13 is not then capable of conveying a line signal as it otherwise would were the parts 1 1- and 15 in connection.

Whena connecting plug is inserted in the tion is such that the circuit for the signaling current is established, which circuit may be traced from the upper terminal of the calling generator 24, to the switch arm 25,, the normal contact of the lower armature switch of relay 26., the sleeve of the plug 0, the line spring 20 of the engaged jack, to the limb 5 of the called line, where the calling current divides. a suiiicient portion passing through the called subscribers hell 3 by way of the limb 5, the switch-hook 1, the condenser 6, the limb 4%, the coil 9 of the called subscribers line relay, to the lower terminal of the calling generator 24, to operate the hell 3. When the called subscriber responds, he causes an energization of the relay 26, thereby to disconnect the calling generator 2 1 from the called subscribers line, said relay'26 having an armature switch 26. rovided with a normal contact that follows the armature switch 26 in its movement until said armature switch engages its alternate contact, whereupon another circuit is closed through the relay 26 that is maintained closed until broken, upon the withdrawal of the plug 0 from its engaging jack. Glaims upon the novel signaling. and ringing features herein illustrated are included in a copending application.

aoaaese I and generally the behavior thereof when a 'call is initiated atthe exchange A for a line terminating at exchange B, I will now describe the features of the system herein shown which form the subject matter of my present invention, it being understood that any suitable equipmentmay be employed at the exchangesA, and B with which the novel features of my invention are adapted for cooperation. When the operator "at exchange A inserts the plug of a cord circuit a in the jack 6 of a trunk line all e, for the purpose of connecting a calling line terminating at exchange A with a called line terminating at exchange B, said operator at exchange A, by .the manipulation of a suit-' able ringing key, includes the ringing generator F in bridge of the sides d 001:, the trunk line circuit, thereby occasioning the operation of the drop signal device 1 located in front of the operator having charge of the plug 0, the signal device f preferably including a shutter which is allowed to fall when said signal device receives current from the generator 7. The signal device 7' Constitutes a clearing-out signal device or supervisory signal device. The energizing circuit for the signal devlce 7 may be traced from the sleeve side of the inserted plug belonging to the set a, to the strand 6 of the trunk circuit which is conductively connected with the sleeve 6 of the trunk line jack to the signal device f through the condenser F, to the normal contact of the armature switch 9, to the tip contact of the trunk line jack at exchange A, to the tip of the plug received by said jack, thence to the generator of alternating current The operator, in response to the signal conveyed at 7, throws her manually operated listening key to the answering position, in which position the contact springs h h are spread apart, thereby to-connect said contact springs with their alternate contacts, eachspring having an alternate contact which constitutes the terminal of the operators telephone receiver 72 Having ascertained the connection'desired, the operator inserts the plug 0 within the jack of the called subscriber (for exam ple, the line P), with results that have hitherto been described and which are set forth in my said co-pending application.

[One of the objects of my present invention is to provide means for preventing the operation of the clearing-out or supervisory signaling apparatus -present in the cord connecting outfit mthat formsa part of the connection between the calling subscriber whose line terminates at exchange A and the called subscriber whose .line terminates at exchange B, whenever the trunk operator deems it desirable to do so, whereby the operation of such supervisory apparatus as i sociated with such cord almay be prevented,

even though the called subscriber" has restored his receiver upon its switch-hooker v the'operator has withdrawn the plug from connection wit h the called subscribefisi line. This feature of my present invention be comes of advantage when either the called subscriber P or the trunu operator, realizing;

that it is desirable to have the calling subscriber connected with another line instead ofthe linc P, may bring about such a new connection without thereby apprising. the operator at exchange Agof therfactthat the subscriber P has restored his telephone re. ceiver upon its switch -hoolr or that the trunk line operator :hadwithdrawn theplug v 0. The .supervisory' or clearing-oiitapparains associated" with tl ccord circuit wat the exchange A is so well known as hardly to require description, the supervisory "apparatus illustratedbein one of several types I that maybe einploye in practising my invention The form of signaling apparatus indicated includestwo supervisory relays a a the relay abBlIlg'fiSSOClfliGd with the an.

sweiing end of the linlncircuit a and the relay a being-shown in association with the connect ng end of the ,link circu t a. i The armatures of these relays, when inert, concalled subscriber, is prevented by a inietalceiv er'2,the impedance coil 8, and the titllic connection between the sidcs of, the tele i phone circuit established at the called station when the telephone receiver is removed from its switch-hook (this metallic .connection, inthe embodiment of the invention illustrated, including the transmitter 7 ,re

switch-hook 1), I provide a substitute inetallic connection which is bridged across the trunk strands (Z and a when the trunk operator knows that the called subscriber is liable to restore his telephone upon its switch- ,hook or when the trunk operator about to withdraw'the plug-.0 (and only. in case the trunk operator does not desire to have a disconnect signal sent in to the exchange'A),

to which end I employ a switching device including a spring 6 permanently connected with a section of the side (l of the trunk line, said contact spring ihaving a contact normally separated therefrom and which constitutes a terminal of thebridge conduc'tor which I import into the system for the purpose above stated, which bridge conductor includes an impedance device and has its other terminal connected with the- -sidesof the trunk circuit.

gagement.

'tliushas lhrce-piiisitions, one, the ansvi'cring position, in whichthc operator is adapted to with the called subscriber without ting the voice currents to pass to the exside 6 of the trunk circuit, whereby when the switch spring 2' is actuated; abridge is connected across the sides of the trunk circuit,1in which bridge the impedance device 2' is includedrforthe purpose of preventing voice currents from being shunted across the For sake of convcnience,,tlie switching device 2' is mechanically mounted upon a spring lover of the operators listening key is, the lever selected being one of the two lovers shown upon the left of the listening key/ c, which, when 0perated, serve to include tlie'-'o 1ieratoi"s tele phone set incircuit, so that she may con:

verse with the called subscriber to the 622- clusion of the calling su'liscrihcnand the calling subscribcrs operator, the opoiator allowing her listening key to remain in its holding position, in which theretardin derice 0, is included in bridge 111 case she 18 advised by the called party to connect the lincand to-engage said plug'witli the jack of another line, the operator still allowing the listening key to remain in this holding positionuntil-tlie operator has inserted a plug in the jack of the newly called party, whereupon-the operatormay restore her telephone key to its normal position, for

i'casonswhich will hereinafter he Set forth.

The operator may also, if she desires, perform -other pr duties that her listening key is in the holding position and while the plug 0 is out ol? jack en- 'Ihc operator s listening key listen tothe wants of the calling subscriber conveyed either by the calling subscriber or the calling subscribefls operator, in which answering position the switch springs ii are spread apart to bridge the operators telephone set /i across the sides of the telephone circuit; two, the normal or central position, 'ii wliich the operators telephone is cut out of circuit; and, three, the holding position, in which the switch parts at the left oi the key 7c are operated to include the impedance device 121 in bridge of the trunk sides, there by to hold or prevent the operation of the clearing-out or supervisory apparatus associated With'lthe connecting end of the cord circuit a/that would otherwise be operated,

when the plug 0 is withdrawn from its jack or the called subscriber has restored his re- .QQIVG'I upon its sw tch-hook.

Nhen the telephone key l: is in the holding position, the operator is adapted to talk change A, as has been stated, and when the telephone key fi is iiitlie answering position (the right-hand position), I desirably c0ndu ing the time permit with theportion of the trunk line extending to the exchange A, so that the trunk operator is not able to bridge her telephone in the combined circuit extending between two connected subscribers.- To this end, I include the armatureswitches Z and their normal contacts in serial relation with the listening key springs ]L,'so thatuwhen the contact of the armature switch 9 with the contact opposed to the spring t' and inasarmature switches are unattract'ed, the opera tors'telephone may be included in circuit when the listening key is thrownto its an' swering position,-there being provided an electro-magnet m for operating the switches Z Z when the plug-c is inserted within the jack oi a called subscriber, to prevent the operator?s telephone from being included in circuit when the listening key is is in the" answering position, so that the operator may only listen to the called subscriber after a trunk line connection has been put up, for

the purpose of securing secrecy of service.

The circuit for the magnet m which is closed by the plug 0 when connected with a called line, may be traced from the upper terminal of the battery 11, through the winding of the magnet m, the body portion of the plug 0, the thimble 15, to the lower terminal of said battery. lVhen the magnet m'is energized and the switchesnre thereby attracted, the trunk operators circuit is opened at Z, securing the results specified, the normally engaged contacts of the switches Z being in serial relation with the contacts of the key 721 and furnishing the means whereby these latter contacts are connected with the talking sides of the trunk circuit.

A relay n is included in circuit when the called subscriber responds, so that the armature switch 9 is attracted to place the lIldl cator f in open. circuit, to prevent said indicator from being again operated until the relay n is d'ecnergized. The circuit for relay or magnet 12 may be traced fromv the upper terminal of the battery 11, through the winding of the magnet a, to the sleeve 1 of the plug a by way of the now attracted of the trunk circuit.

9 governed by-the elcctro-magnet a when lower armature switch of the relay 26, the sleeve spring :20 of the called subscribers jack, over the line of the called subscriber, through the winding 9, to the lower terminal of the battery 11. The relay 26 is included in a local circuit after the plug 0 has been inserted, which plug 0 governs said local circuit, the relay 26 bringing the relay n into the control of the subscriber P and permitting the subscriber P to retain such control until the plug 0 is withdrawn. hen the electro magnet a is thus energized, its topmost. and lowermost armature switches are actuated tocomplete the sides The armature switch actuated, engages an alternate contact provided therefor, to establish a bridge across j ,a eae a the sides of trunk ife i t wh n rP ifi-e vent the operation of the clearing-out or supervisory signal associated, with, the" con i necting end of the cord circuit a (said supervisory or' clearing out signal also being similarly held in case the subscriber P were a calling subscriber), and inorder ,to avoid the necessity of employing an' additional, bridge conductor, I connect the alternate much as said armature switch 9 is connected with the switch spring 71, the impedance device '6 is included in bridge betweenthe sides of the trunk circuit when the,

armature switch g engages its alternate contact. In case the trunk operator is'to' re-' ceive the 1 knowledge ofthe wants of the ciated with that end of the cord circuit a i which engagesthe trunk line jack and at the exchange A.

After the trunk operator inserts the plug c in the jack of a called line, the operator restores her listening key to its central or side posit-ion, in which t-heterminals of the impedance device i associated with the listening key are disconnected from the springs of the listening key, and in order to prevent the operation of the clearing-out'or supervisory signal device at the ringing end of the cord circuit a, still another terminal for the impedancedevice 2' .is brought into connection with the side d of the trunk cir cu-it, this last terminal of the impedance de vice 2' being the alternate contact of the armature switch Z. The alternate contact'of the armature switch Z is connected with'the impedance device 2' by way of the uppermost armature switch of the relay'26 and the contact engaging said armature switch when said armature switch is in its unattracted position. The magnet 26 is energized when thecalled subscriber responds, as has been set forth, so that the bridge containing the impendance device 2' is again broken so far as the alternate contact of the switch Z is concerned, but inasmuch as the magnet a 1s energized when the called subscriber re 7 sponds, the bridge for the impedance device 6 is established at the alternate contact of the armature g, as has been described.

I speak of preventing the operation of the clearing-out or supervisory signal device at the right-hand end of the cord circuit a,

meaning thereby that such signal device is prevented from presenting a clearing-out or S11}?(3i\ls()1'y signal. i

Itwill be observed in the system I have described, that the clearing-out or disconnect device'at the right-hand end of the cord circuit a isgoverned by the. metallic connection e'tl'ected at the station 1 or other called station when the receiver thereat is removed, this metallic connection being-in continuous circuit relation with the magnet a when the called subscribers receiver is removed from its switch-hook, the magnet a governingthe bridge which is adapted to prevent or permit of the operation ofsaid clearingout or supervisorysignal.

In the preferred embodimentot' 1ny invention, I divide the trunk circuit into two telephonical'ly,united sections that are not inetallically continuous, there being employed condensersb 11 in the sides of the trunk circuittor separating each side into two parts so far as direct currents'arc conwith the trunk conductors (Z c on those sides- 3'0 ce1'ned,but preserving the continuity of each. side of the cord circuit so-far as tele-.

phonic currents are concerned.

The bI'lClg" conductor lncluding the'impedance dev ce i .18 "adapted-for connection of the condensers 0 19 that are connected or adaptedfor connection metalli ally with the trunk line jackat thecxchange A. By this arrangement I am enabled toeinploy batteriesof suitable voltages for the trunk line 'clr'cuits and the exchangeequ pment at A,

whether such voltages are similar or wide apart in values I, furthermore, am enabled to eliminate all grounds from the battery terminals. The irnpedancerl is normally,

grounded through the signal lamp q byway of the normal contact of anarmature switch I belonging to relayj Whenfthetrunk line operatorat C' desires to signal the :5 cuit' einploved for the purp o scs'ofestablishswitcli' ;-boa1'd operator at A, the trunk line operator, .as-a. consequence of the operation .0f flier: listening-ltey,- completes circuit through thei lamp 9,.Ivvliich maybe traced from-the grounded battery at exchange Af 1' throughthe lamp" g,the' armature switch 1. i

, '2', to ltlrefgrounded armatureswitch qt. means of the system; illustrated, the trunk line" operator may signal. the exchange ,op-

of the relay q, the-impedance 2";,,switch part By orator and the exchange operator'rnay' signal the trunk lineoperator"withoutthefuse ofi special orderwires' q'lhe trunk line equip-. merit enters into the apparatus employed :for

effecting transmission of signalingcurrent from the trunk lineoperator tothe exchange operator, and Qvic'e versa, whereby-special or der wire equipment -lI1 tQlfVt3Illll I between rent from this generator F is permitted to t averse a pal-tot thetrunk wlienjzhe key a v -1s operated, In order to worl; the signal deing telephonic connection between telephone lines terminating at different exclianges,'to enable conversation between the trunk line operator and exchange operator-aiul to, enable each of these operators to signal the other.

In some of the claims the expression twoway has been used in connection with the expression trunk circuit, such expression having the meaning here set forth.

It will be seen'that there is another object 'accomplished'by the provision of the bridge means for the trunk line jacks, as any well knownnieans may becmploycd for the purpose;

J'lhe magnet 26, when included in local circuit, prevents the re-inclusion of the'generator. 2st in circuit with the trunk until the plug 0 has been withdrawn. If the operator at exchangeA should happen to select a trunk circuit which tests free and which still has its plug sin a jack,.su'ch operatoratexchange A In'ay'operate the signaldevice f by means of her calling key a, but will not operate the signal receiver of the linestill connected with the selected trunk by the trunk plug-c. Thus the generatorf at the exchange A.is prevented from being ineluded in circuit with the signal receiver 3 at station P by the magnet 9.6, alth0'ugh curvicef H Imam aware that two-way trunk circuits .hav eloeen hitherto proposed, but they have notbeen used in number, 'becausein their use, objections have been encountered which are cured by the system of my invention.

' While I have herein shown and particularly. described the preferred embodiment of my invention, I do not wish'to be limited to the precise" construction and arrangement set forth, aschanges may readily lie-made without depart ng from the spirit of theinventioni l v Having thus. described my invention, I claimv asfnew and desire to secure. by Letters "Patent the following [1. \ytelepho'ne exchange system including telephone lines extending from substations to dill' erent exchanges, a voice-current-emiveying'two-tvay trunk circuit fouuniting said lines in conversation, said trunk circuit beingnformed in sections that areu'n'unitcd oaacsa tion with one of said sections of theetrunk circuit in the process of establishing a connection through said latter exchange, means associated with the other section of said .trunk circuit for governing the aforesaid supervisory or clearing-out signaling apparatus, and operator-controlled switching mechanism associated with the section of the trunk circuit that is notmetallically connected with the supervisory or disconnectsignaling apparatus, for preventing false.

operation of said clearmg'out or supervisory signallng apparatus.

2. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-current-conveying trunk circuit for uniting said lines in conversation, said-trunk circuit being formed in sectionsthat are ununited metallically but are united telephonically, clearing-out or supervisory signaling apparatus atone exchange adapted for association with one of said sections of the trunk circuit in the process of establishing a connectlon through I said latter exchange, means associated with the other section of said trunk circuit for governing the aforesaid supervisory or clearing-out signaling apparatus, operatorcontrolled switching mechanism jointly controlled by the terminal-connecting element of the link circuit, which connecting element is not metallically connected with the super-' visory or clearingeout signaling apparatus andis associated with the aforesaid means, and a switching device adapted to co-act with said terminal element, said switching mechanism serving, when operated, to prevent false operation of said clearing-out or supervisory signaling apparatus.

3. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-current-conveying trunk circuit for uniting said lines in conversation, said trunk circuit being formed in sections that are un-united metallically but are united telephonically, clearing-out or supervisory signaling apparatusat one exchange adapted for association with one of sald sections of the trunk circuit in the process of establishing a connection through said latter exchange, means associated with the other section of said trunk circuit for governing the aforesaid super- 4 visory orclearing-out signaling apparatus,

a source of ringing current, subscribercontrolledswitching mechanism for including the same in circuit relation with the called station that is connected with the section of the link circuit in association with theaforesaid means, and which said section of the link circuit -is not metallically connected with the supervisory or disconnect signaling tion of said clearing-out or supervisory sig naling apparatus.

4. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-current-conveying trunk circuit for uniting said lines in conversation, said trunk circuit being formed in sectionsthat are un-united metallically but are united telephonically, clearing-out or supervisory signaling apparatus at one exchange adapted for association with one of said sections of the trunk circuit in the process of establishing a connection through said latter exchange, means associated with the other section of said trunk circuitffor governing the 'aforesaidsupervisory or clearing-out signaling apparatus, a signal device associated with the trunk circuit and operable'from the 'exchangeto which the trunk circuit extends, and relay mechanism at the trunk circuit station for dissociating said signal device, said relay mechanism including a switching device that serves to permit the operation of the aforesaid means to avoid false operation of said clearing-out or disconnect signaling apparatus.

5. A telephone exchange system including in the process of establishing a connection through said latter exchange, means associated with the othersection of said trunk circuit for governing the aforesaid supervisory or clearing-out signaling apparatus, an operators telephone equipment adapted for connection with the section of the trunk ios circuit which is metallically connected with said supervisory or disconnect signaling apparatus, and electromagnetic mechanism governed by atrunk circuit apparatus, for dissociating said operators telephone from the trunk circuit, said electro-magnetic mechanism including a switching-device that serves to prevent the operation of the aforesaid means, to prevent false operation of said clearing-out or supervisory, signaling apparatus."

6, A telephone exchange system including telephone lines'extending from sub-stations to difierent exchanges, a voice-current-conveying trunkcircuit for uniting said lines in conversation, said trunk circuit .being formed in sections that are un-united metallically but are united telephonically, cleartion through said latter exchange, meansassociated with the other section of said trunk circuit for governing the aforesaid telephone lines extending from sub-stations SHJCFVlSOl" or clearin -out si nalin a )at b O l 2.:

ltd

ratus, an operators telephone equipment adapted for connectlon with the section of the trunk circuit which is metallically connected with said supervlsory or disconnect s gnaling apparatus, and switching mecha veying trunk circuit for uniting said lines in conversation, said trunk circuit bemg formed in'sections that are un-united metallically but are united telephonically, clearing out or supervisory signaling apparatus at one exchange adapted forassociation with one of said sections of'the trunk circuit in the process; of establishing a connection through sa1d latterexchange,,means assocr ated with the-other section ofzsaid trunk circuit for governing the aforesaid supervisory .or' clearing out signaling apparatus,

an, operators telephone equipment adapted ,forconne'ction with the sectioniofthe trunk circuit which is'metallicallyconnected with said supervisory or disconnectsignalingapparatus, and switching mechanism "for ineluding the operators telephone equipment in circuit relation with the answering end 1 of the trunk circuit, and serving to prevent effective operation" of the aforesaidineans 515 to preventvfalse operation of said clearing out or supervisory signaling apparatus. p 8. 'A'tele'phone exchangesystexn ln'cluding telephone lines extending. from sub-stations. ,to different exchanges, a voicc-current-con veying' trunk; circuit for uniting said lines I in conversation, said trunk-circuit-being formed in sections thatare un-united InetaL lically but are'united telephonically, clearfing-out: or supervisory signaling apparatus Q3551 one of said sections of the trunk circuit-in at one exchange adapted for association with the pr-Iocess -of establishing a connection through said latter exchange, 'means associatedfwitlr the other section of saidtrunk circuit vfor governing thejaforesaid super= visory orclearing-ont signaling apparatus,

, an operatorfs telephone equipment adapted for connection with the section of the trunk x i circuit whichis metallically connected with said supervisory or clisconnec't'signaling apparatus, and switching mechanism for including the operators telephone equipment in circuit relation with the connecting end of the trunk circuit and serving to prevent etl'ective operation of the aforesaid means,

to prevent false operation of said clearing out or supervisory signaling apparatus.

S). A telephone exchange system including to dilt'ercnt. exchanges, a VOiUQ-(ftlll'Ollt-COI];

veying trunk circuit for uniting said lines in convcrsatimi, said truult circuit being formed in sections that are un-united metallically but a re united tclcphonical1y. clearingout or supervisory signaling apparatus at one exchangeadapted for association with one of and switching mechanism for limiting the operato1"stelephone equipment to association with the answeringcnd oi the trunk circuit and serving to prevent operation of the atorcsaid means to prevent :lalse operation of said cleaning-(nitor siuwrvisory signaling apparatus. i v 1 .10. A telephone exchange system including telephone lines extending from suhstations to ditl'crent exchanges, a voice-current-conveying trunk circuit for uniting said lines in-conversation, said trunk circuit being formed in sections that are un-unitcd mejtallically but are united telcphonically, clearing-out or supervisory signaling ap 'iaratus at one exchange adapted for association with oneof said sections of the trunk circuit in the process of establishing a connection through said latter exchange, means associated with the other section of said trunk circuit for governing tl'ieaforesald-superv1- -sory or clearing-out signaling apparatus, an operators telephone equipment adapted for connection with the section of the trunk circult WlllChs metalhcally connected with f said supervisory or disconnect signaling ap- Iqparatus, and switching mechanism for limiting the operators telephone equipment to associationwith the connecting end of the trunk circuit and serving to prevent operationiof the aforesaid means to prevent false operation of said clearing-out. or supervisory signaling apparatus.

11. A telephone exchange system including telephone'lines extending from sub-stations to different exchanges, a voice-mlrrentconveying trunk circuit for uniting said lines in conversation, said trunk circuitbeing formed in sections that are Lin-united me- .deviee associated with the trunk circuit and operable from the exchange to which the trunk circuit extends, and relay mechanism at the trunk circuit station for dissociating said signaling device, said relay mechanism also governing the said bridge.

12. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-current conveying trunk circuit for uniting said lines in conversation, said trunk circuit beingformed in sections that are un-united meta-ll-ically but are united telephoni'cally, clearing-out or supervisory signaling apparatus at one exchange adapted for associa tion with one of said sections of the trunk circuit in the process of, establishing a connection through said latter exchange, a bridge adapted for association wit-h the latter trunk circuit section and governed for the purpose of preventing false operation of said clearing-out or supervisory apparatus and permitting the proper operation of said clearing-out or supervisory signaling apparatus by other apparatus, a switching device for opening and closing said bridge conductor, an operators telephone equipment adapted for connection with the section of the trunk circuit which is meta-llically con 'nected with said supervisory or disconnect signalingapparatus, and ele'ctro-magnetic mechanism governed by a trunk circuit apparatus, for dissociating said operators tele phone from the trunk circuit and governing said bridge.

13.. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-currentconveying trunk circuit for uniting said lines in conversation.- said .trunk circuit being formedin sections that are nil-united Inetallically but are united telephonica1ly, clearing-out or supervisory signaling apparatus at' one exchange adapted for associavtion with one of said sections of the trunk circuit in the process of establishing a, conuection through .said latter exchange, a

, bridge adapted for association with the lat ter trunk circuit section and governed for,

the purpose of preventing false operation of said clearing-out or supervlsory apparatus and permitting the proper operation of said clearing-out or supervisory slgnaling apparatus by other apparatus, a switching device for opening and closing said bridge conductor, an operators telephone equipment adapted for connection with the section of the trunk circuit which is metallically con,- nected with said supervisory or disconnect signaling apparatus, and switching mechanism for including the operators telephone equipment in circuit with the trunk circuit and serving to govern said bridge.

14. In a telephone exchange system including telephone lines extending from subs stations to different exchanges; a voice- -current-conveying trunk circuit for uniting said lines in conversation, said trunk circuitbeing formed in sections that are un-united metallically but are united telephonically, clearing-out or supervisory signaling apparatus at oneexchange adapted for association with one of said sections of the trunk circuit in the process of establishing a con-" nection through said latter exchange, a

bridge adapted for association with the lat ter trunk circuit section and governed for the purpose or preventing false operation of said clearing-out or supervisory apparatus and permittingthe proper operation of said clearing-out or supervisory signaling apparatus by other apparatus, a switching device for opening and closing said bridge conductor, an operators telephone equipment adapted for connection with the .section of the trunk circuit which is metallically connected with said supervisory or disconnect signaling apparatus, and switching mechanism for including the operators telephone equipment in ,circuit relation with the answering end of the trunk circuit and serving to govern said brldge.

15. A telephone exchange system inch1ding telephone lines extending from sub-stations to different exchanges, a voice-currentconveying trunk circuit for uniting said lines in conversation, said trunk circuit being formed in sections that are un-united I'netallically butare united, telephonically, clearing-out or supervisory signaling apparatus at one exchange adapted for association with one of said sections of the trunk circuit in the process of establishing a connection through said latter exchange, a bridge adapted for association with the latter trunk circuit. section and governed for the purpose of preventing false operation of said clearing-out or' supervisory apparatus and permit-tingthe proper operation of said clearing-out or supervisory signaling apparatus by other apparatus, a switching device for opening and closing said bridge conductor, an operators telephone equipment adapted for connectionwith the section of the trunkcircuit which is metallically con nected with said supervisory or disconnect ,to diil'erent exchanges, a voice-current-conveying trunk circuit for uniting said lines in conversation, said trunk circuit being formed in sections that are un-united metallically but are united telephonically, clearing-out or supervisory -signaling apparatus at one exchange-adapted for association with one of said sections of the trunk circuit in the process of establishing a connection through said latter exchange, a bridgeadapted for association with the latter trunk circuit section and governed for the purpose ofpreventing false operation of said clearing-out or supervisory apparatus and permitting the proper operation of said clearing-out or supervisory signaling apparatus by other apparatus, a switching device for opening and closing said bridge conductor, an operators telephone equipment adapted for connection with the section of the trunk circuit which is metallically connected with said supervisory or disconnect signaling apparatus, and switching mechanism for limitlng the operators telephone equipment to association with the answerlng end of the trunk circuit and serving to govern said bridge.

17. A telephone exchange system including telephone lines extending from sub-stations to different exchanges, a voice-currentcdnveying trunk circuitfor uniting said lines in conversation, said trunk circuit being formed in sections that are un-united metallically but are united telephonically, clearing-out or supervisory signaling apparatus at one exchange adapted for association with one of said sections of, the trunk circuit in the process of establishing a connection through said latter exchange, a bridge adapted for associationwith' the 1atter trunk circuit section and governed for the purpose of preventing false operation of said clearing-out 'or supervisory apparatus and permitting the proper operation of said clearing-out or supervisorysignaling apparatusby other apparatus, a switchmg device 'for opening and closing said bridge conductor, an operators telephone equipment adapted for connection with the section of the trunk circuit which'is metallically connected with said supervisory or disconnect signaling apparatus, and switching mechanism for limiting the operators telephone equipment to associationwith the connecting end of the trunk circuit and serving to overn said-bridge.

18. Ate ephone exchange system includ-t ing telephone lines extending from substations to dilt'erent exchanges, a voice-currenteonveying trunk circuit for uniting said lines in conversation, said trunk circuit being formed in sections that are un-united 'metallically but are united tclephonically,

clearing-out 'or supervisory signaling apparatus at one exchange adapted for association with one of said sections of the trunk circuit 111 the process of establlshlng a connectlon through said latter exchange, means associated with the other section of said trunk circuit for governing the aforesaid supervisory or clearing-out signaling apparatus, and operator-controlled switching mechanism associated with the section of the -trunk circuit that is not metallically connected with the supervisory or disconnect slgnaling apparatus, for preventing false operatlon of SillCl clearmg-out or supervisory to the first exchange, a signal device in the trunk circuit, means at the second exchange for impressing signaling current upon telephone lines extending thereto and upon said trunk circuit-signaling device, means at the first exchange for impressing signaling current upon telephone lines extending thereto, and means for preventing operating signaling current from passing to a telephone line connected with the trunk circuit at the first exchange when said means at the second'exchan e is operated, without preventing the signa ing current passing to said trunk circuit-signaling device. i

20. A telephone exchange system including telephone lines extending from sub-stations to one exchange, telephone lines extending from substations to a second'exchange, a trunk circuitextending between said exchanges and having operator-controlled means at the first exchange for connecting it with telephone lines extending to the first exchange, a signal device in the trunk circuit,means at the second exchange for impressing signaling current upon telephone lines extending thereto and upon said trunk circuit-signaling device, means at the 'first exchange for impressing signaling current upon telephone lines exten ing thereto, and electromagnetic mechanism governed by the trunk circuit-signaling device for preventing operating signaling current from passing to a-telephone line connected with the trunk circuit at the first exchange when said means at the second exchange is operated 1-. .ahout preventing the signaling current passing to said trunk circuit-signaling device.

21. A telephone exchange system includ- 5 ing telephone lines extending from sub-stations to one exchange," telephone lines extending from sub-stations to. a second exchange, a trunk circuit extending'b etween' said exchange and having means governed today the operators listening switch at the first exchange for connecting it With telephone llnes extending to thefirst exchange, link c rcuits at the second exchange for uniting lines extending thereto, clearing-out or ELMER R. CORXVIN.

I Witnesses:

- G. L. CRAGG, LE. S'rnon. 

